Karen Dobkins
Today's Notes:
http://psy.ucsd.edu/~kdobkins/HDPnotes.html
OUTLINE
Red/Green vs. Black/White
2) PATTERN VISION (stripes, Snellen acuity)
3) MOTION PERCEPTION (if thereís time)
Why Study Development?
#1: What are the Perceptual consequences of Neural changes during Postnatal Development?
Neurons and Connections: transient, then pruned
Myelination: matures very slowly (up to 16 years)
Infant Photoreceptors
- Immature Morphology ->
do not resolve well
(will come back to later)
#2: Clinical applications
e.g., Dyslexia
Magnocellular -> Motion Processing
Parvocellular -> Color Processing
METHODS
How do we get babies to tell us what they see?
First: some background in psychophysics
Grating Stimulus
Spatial Frequency (SF) and Contrast
Detection Task:
2-AFC: Can you see it? Left or Right?
How well can you see it?
INFANTS: Forced-Choice Preferential Looking (FPL)
FPL stimulus (babies tend to look at patterns)
FPL Testing with Adult Observer
What the baby sees: Fun Stimulus, FPL Stimulus
Infant PSYCHOMETRIC FUNCTION
Threshold (contrast yielding 75% correct)
Sensitivity = 1/thr
Why use sensitivity?
COLOR VISION IN INFANTS
Testing this proposal: "Infants donít see colors well"
RED/GREEN stimuli, how well can they see?
Luminance (Black/White)
vs. Chromatic (Red/Green) Contrast
CHROMATIC vs. LUMINANCE DATA
Why people thought infants donít see COLORS
(donít use PASTELS, thatís low contrast!)
COLOR vs. LUMINANCE thresholds in I & A
COLOR:LUMINANCE ratios in I & A
A MYTH DISPELLED
PATTERN VISION
Acuity,
Spatial Contrast Sensitivity Function
Develops Slowly
Photoreceptor Morphology -> Overall Sensitivity
Photoreceptor Spacing -> Overall
Acuity
TEMPORAL VISION: MOTION
Temporal Contrast Sensitivity Function:
Same stripe width of grating, different
SPEEDS
Infants and Adults
Contrast Sensitivity best at around
22 deg/sec
Similar speed tuning!
Why might motion processing mature
relatively fast?